The present invention relates to a method for screening for risk of Alzheimer's disease in a patient, and to a transgenic mammal carrying a mutated human gene associated with the development of Alzheimer's disease.
Alzheimer's disease is a form of localized amyloidosis characterized by cerebral cortical amyloid plaques, neurofibrillary tangles, and amyloid deposits within the walls of leptomeningeal vessels. Although most cases of Alzheimer's disease are sporadic, kindreds with autosomal dominant inheritance of the syndrome suggest that a single mutation may be important in pathogenesis.
Hereditary or familial Alzheimer's disease is an autosomal dominant form of localized amyloidosis. Patients with hereditary Alzheimer's disease typically develop three pathologic lesions: (i) senile plaques in the cerebral cortex characterized by a centeral amyloid core surrounded by dystrophic neurites; (ii) neurofibrillary tangles; and (iii) congophilic angiopathy of the leptomeningeal vessels. The amyloid deposits in the senile plaques and in the blood vessel walls contain a fibril subunit protein of 39 to 43 amino acid residues See, G. G. Glenner and C. W. Wong, Biochem Bisophys., Res. Commun., 120, p. 885 (1984)!, which is a portion of the carboxyl terminus of the amyloid precursor protein (APP). Sequence analysis of cDNA clones of APP has shown that there are multiple forms of mRNA which are the result of alternate splicing of a transcript from a single gene. See, J Kang et al., Nature, 325, p. 733 (1987 ); P Ponte et al., Ibid, 331, p. 525 (1988 ); R. E. Tanzi et al., Ibid, p. 528; N. Kitaguchi, Y. Takahashi, Y. Tokushima, S. Shiojiri, H Ito, Ibid, p.530; N. Kitaquchi et al., Biochim, Biophys. Acta. 1039, p. 105 (1990 ); and S. Yoshikaii, H. Sasaki, K. Doh-ura, H. Furrya, Y. Sasaki, Gene 87, p. 257 (1990 ). Although the sequence of the APP gene from some patients with either sporadic or familial Alzheimer's disease is normal See, D. Goldgaber, M.I. Lerman, O. W. McBridde, U. Saffotti, D. C. Gajdusek, Science 235, p. 887 (1987 ); R. E. Tanzi et al., ibid, p. 880; N. K. Tobakis, Sci. Ramakrishna, G. Wolfe, H. M. Wisniewski, Proc. Natl. Acad. Sci. U.S.A., 84,p. 4190 (1987 ); H. G. Lemaire et al., Nucleic Acids. Res. 17, p. 51 (1989 ); and M. P. Vitek et al., Mol. Brain Res. 4, p. 121 (1988 ) !, a cytosine to thymine missense mutation in the membrane-spanning domain of the APP gene (causing a valine to isloeucine change in the corresponding) amino acid sequence of the encoded APP) has been identified in patient from several families with familial Alzheimer's disease. See, A. Goate et al., Naure 349, p. 704 (1991 ).
In the applicants work, analysis of DNA from a family with autopsy-proven Alzheimer's disease revealed a single amino acid substitution (phenylalanine for valine) in the transmembrane domain of the amyloid precursor protein. This substitution is caused by a point mutation at nucleotide position 1924 (using the APP695 transcript) of the gene encoding the amyloid precursor protein in which guanine (normal) is replaced by thymine (mutant). This mutation correlated with the presence of Alzheimer's disease in all studied patients. Accordingly, one embodiment of the invention relates to a method for screening for risk of Alzheimer's disease in a patient. The method includes the step of assaying for a guanine to thymine point mutation at position 1924 of the patient's gene encoding the amyloid precursor protein.
The applicant' discovery also provides access to transgenic non-human mammals, preferably rodents such as mice, harboring an expressable gene sequence encoding human amyloid precursor protein having a phenyalaine for valine amino acid subsitution in the transmembrance domain of the amyloid precursor protein. Access is also provided to vectors containing the above-noted gene sequence which can be used to create transgenics for study or protein expression (i.e. for production and recovery), and to the above-noted mutant amyloid precursor protein (with the phenylalanine for valine substitution) in substantially pure form.
Additional objects, advantages and embodiments of the invention will be apparent from the following description and appended claims.